This invention relates to a device for holding the end portion of a band-like material.
A conventional device for holding the end portion of a band-like material includes a frame and a suction attraction bar which is secured to the frame. A vacuum suction passage extends in the longitudinal direction of the bar and a plurality of suction holes communicate with the vacuum suction passage and are open in the outside surface of the suctional attraction bar. The holes are located at a spaced distance from each other in the longitudinal direction of the bar. The suctional attraction bar is pushed on the end portion of the band-like material and air is thereafter sucked through the suction holes and the vacuum suction passage so that the end portion of the band-like material is held through suction attraction. All the suction holes of the device communicate with the vacuum suction passage. For that reason, there is no problem if all the suction holes are closed by the band-like material at the time of the suction attraction thereof. However, if the width of the band-like material is so small that some of the suction holes are open to the atmosphere, there is a problem that the pressure in the vacuum suction passage rises to reduce the suctional attraction power of the device to let the suction-attracted band-like material deviate relative to the suction attraction bar or come off it.
It is possible to provide the suction holes with valves and open or close the valves depending on the width of the band-like material, in order to solve the above-mentioned problem. However, if such is done, there are other problems in that the control and thus modified construction of the conventional device are complicated and the cost thereof is increased.
Since there is a limit to the suctional attraction power of the conventional device, there is still another problem that the band-like material deviates relative to the suctional attraction bar or comes off it if a strong external force acts to the band-like material.